L02 atomic building blocks

Question 1

What are the primary types of bond?

Answer 1

Metallic
Covalent
Ionic

Question 2

What are metallic bonds?

Answer 2

Atoms readily give up valent electrons, creating a sea of delocalised electrons to move freely through the solid

Question 3

Characteristic properties of metallic bonds

Answer 3

High electrical conductivity
High thermal conductivity
Opaque (free electrons may absorb light/photons, issues with curing)
Lustrous (free electrons may remit light, through electrons jumping to different energy levels, making them appear shiny coloured/tinted)
Leads to a crystalline arrangement in metals

Question 4

What are covalent bonds?

Answer 4

Atoms share electrons, the atoms approach and orbitals overlap

Question 5

What does highly directional covalent bonds mean?

Answer 5

Electrons contained within overlapped orbitals with geometrical constraint

Question 6

What are characteristic properties of covalently bonded structures?

Answer 6

Very strong and highly directional
Insulators
Bond forms basis for polymers

Question 7

What are ionic bonds?

Answer 7

Exchange of valent electrons. Loss and gain of electrons, opposite electrical charge, electrostatic attractive forces. Non-directional

Question 8

Characteristic properties of ionic bonds?

Answer 8

Very stable (high ionic bond strength, more inert)
Heat resistant and insulators as solids
Electrical conductors in solution (disassociate to constituent ions in solution)
Bond forms basis for ceramics and glasses

Question 9

What property of glass ionomer cements can help remineralise enamel?

Answer 9

They can leach fluoride ions

Question 10

What is a bond energy?

Answer 10

Strength of a bond

Question 11

What is the order of bond energies for the different types of bonds?

Answer 11

Covalent bonds have the highest energy, then ionic and metallic

Question 12

What attractive forces hold atoms together?

Answer 12

Primary and secondary bonding

Question 13

What is mutual repulsion?

Answer 13

Forces balance
Configuration of minimum energy
Close-packed arrangement

Question 14

Energy separation curve

Answer 14

Page 6 of notes

Question 15

What does an energy separation curve show?

Answer 15

Defines the energy state when 2 atoms combine themselves, for a particular element, bond length and bond energy

Question 16

Describe the energy separation curve from right to left.

Answer 16

2 atoms are far apart, with weak atomic attraction
As they get closer together, attractive force increases, until it reaches a minimum energy state/a 0 force
As they get closer again, they will repel each other
When bonds are formed, energy is release and must be absorbed when bonds are broken

Question 17

What is melting temperature of a material determined by?

Answer 17

Bonding energy

Question 18

What is elastic modulus (stiffness) of a material determined by?

Answer 18

Shape of energy separation curve

Question 19

What is electrical conductivity of a material determined by?

Answer 19

Inter atomic bond type

Question 20

What is thermal expansion of a material determined by?

Answer 20

Potential energy of the material